ON THE BARYON CONTENT OF THE SHAPLEY SUPERCLUSTER

The Shapley Supercluster is particularly rich in baryons, since it contains many X-ray luminous clusters. Using the relationship between X-ray luminosity and gas mass within 3h50(-1) Mpc radius found for nearby clusters, it is shown that the ratio of the baryon density to the critical density in the 37h50(-1) Mpc core of the supercluster OMEGA(b) > 0.18h50(-1.3). This is much larger than the value obtained from published calculations of cosmic nucleosynthesis, OMEGA(b) = 0.06h50(-2). The high baryon content requires that the supercluster has a total mass overdensity rho/rho-BAR > 2.4, the largest yet established on large (approximately 35h50(-1) Mpc) scales.